Start at the centre letter, and move around the upper triangle in a clockwise direction. Letters follow the alphabetical order in steps of 9 letters at a time. Repeat the same pattern, moving clockwise around the lower triangle, with the letters written in steps of 7 letters at a time.
Start on the upper left hand segment of the left hand circle and move anti-clockwise around it. Then move to the upper left of the central circle and move clockwise, then on to the right hand circle, and again move anti-clockwise. Letters are written in sequence along this path, skipping 3 letters, then 4, 5 and 6, before repeating this sequence.